title: Correlation analysis of dual-energy CT iodine maps with quantitative pulmonary perfusion MRI.
abstract: OBJECTIVE
  To correlate dual-energy computed tomography (DECT) pulmonary angiography derived iodine maps with parameter maps of quantitative pulmonary perfusion magnetic resonance imaging (MRI).
  
  
  METHODS
  Eighteen patients with pulmonary perfusion defects detected on DECT derived iodine maps were included in this prospective study and additionally underwent time-resolved contrast-enhanced pulmonary MRI [dynamic contrast enhanced (DCE)-MRI]. DCE-MRI data were quantitatively analyzed using a pixel-by-pixel deconvolution analysis calculating regional pulmonary blood flow (PBF), pulmonary blood volume (PBV) and mean transit time (MTT) in visually normal lung parenchyma and perfusion defects. Perfusion parameters were correlated to mean attenuation values of normal lung and perfusion defects on DECT iodine maps. Two readers rated the concordance of perfusion defects in a visual analysis using a 5-point Likert-scale (1 = no correlation, 5 = excellent correlation).
  
  
  RESULTS
  In visually normal pulmonary tissue mean DECT and MRI values were: 22.6 ± 8.3 Hounsfield units (HU); PBF: 58.8 ± 36.0 mL/100 mL per minute; PBV: 16.6 ± 8.5 mL; MTT: 17.1 ± 10.3 s. In areas with restricted perfusion mean DECT and MRI values were: 4.0 ± 3.9 HU; PBF: 10.3 ± 5.5 mL/100 mL per minute, PBV: 5 ± 4 mL, MTT: 21.6 ± 14.0 s. The differences between visually normal parenchyma and areas of restricted perfusion were statistically significant for PBF, PBV and DECT (P < 0.0001). No linear correlation was found between MRI perfusion parameters and attenuation values of DECT iodine maps (PBF: r = 0.35, P = 0.15; PBV: r = 0.34, P = 0.16; MTT: r = 0.41, P = 0.08). Visual analysis revealed a moderate correlation between perfusion defects on DECT iodine maps and the parameter maps of DCE-MRI (mean score 3.6, κ 0.45).
  
  
  CONCLUSIONS
  There is a moderate visual but not statistically significant correlation between DECT iodine maps and perfusion parameter maps of DCE-MRI.
authors.affiliation: Jan Hansmann, Paul Apfaltrer, Thomas Henzler, Mathias Meyer, Gerald Weisser, Stefan O Schoenberg, Ulrike I Attenberger, Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167 Mannheim, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Hansmann
authors.forename: Paul
authors.initials: P
authors.lastname: Apfaltrer
authors.forename: Frank G
authors.initials: FG
authors.lastname: Zoellner
authors.forename: Thomas
authors.initials: T
authors.lastname: Henzler
authors.forename: Mathias
authors.initials: M
authors.lastname: Meyer
authors.forename: Gerald
authors.initials: G
authors.lastname: Weisser
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Ulrike I
authors.initials: UI
authors.lastname: Attenberger
keywords: Dual-energy computed tomography; Iodine maps; Pulmonary perfusion; Time-resolved magnetic resonance imaging